1. Field of the Invention
The present disclosure relates to optical networks. In particular, but not exclusively, the present disclosure relates to generating path configuration data for optical networks.
2. Description of the Related Technology
Core optical networks for large Internet service providers may consist of very large numbers of network elements (optical routers, switches, etc.) with complex inter-connectivity. Managing these networks to set up dedicated Multiprotocol Label Switching (MPLS) routes between two nodes is a complex task. As the network size increases, the complexity of calculating these routes becomes a Non-deterministic Polynomial-time hard (NP-hard) problem and finding an exact solution computationally becomes unfeasible. Quite often, a network engineer will plan routes by pen-and-paper.
Simplifications in the network representation may be used to calculate computationally near-optimal routes in these complex networks. New ways to simplify the calculation allow computational path calculations that can yield better results than pen-and-paper optimization.
The well-known Dijsktra algorithm can be used to solve least cost paths through simple networks consisting of a set of nodes and weighted links joining the nodes. Optical networks, whilst consisting of a set of nodes (optical switches, amplifiers, etc.) and links (optical links) there-between, are more difficult to handle because they have added degrees of freedom, for example the use of different wavelengths to transmit data along the same link and the ability of the node to either pass-through the wavelength, retransmit the data over a different wavelength or re-pack the data into a new or existing wavelength.
In one scenario, a wavelength is either passed through an optical node directly, i.e. the ingress wavelength is the same as the egress wavelength. In another scenario, an ingress wavelength is converted to a different wavelength at the egress (which may or may not require repacking/reframing of the data). The former scenario is referred to herein as wavelength pass-through and the latter scenario is referred to herein as wavelength conversion.
One known mechanism for generating path configuration data with least cost routing is to represent the network as a graph, where the network graph is expanded to have separate edges for each available wavelength between two nodes. With a large number of available wavelengths on a single fiber, such an expanded graph representation may become excessively large increasing dramatically the network complexity. In some cases, the added complexity may render least cost routing incalculable within a reasonable timeframe.